n = int(input())            # 输入一个整数
n = str(n)                  # 转为字符串
count =0
for i in n:
    i = int(i)              # 再转为整数用来判断
    if i % 2 != 0:          # 检查是否为奇数
        count +=1           # 累加出现奇数的次数
print(count)








# n = input()
# # 使用列表推导式，并在转换前检查字符是否为数字
# count = sum(1 for i in n if i.isdigit() and int(i) % 2 != 0)
# print(count)




# n = input()
# print(sum(int(i) % 2!= 0 for i in n))